In conventional hydroelectric power generating stations, the energy developed by the water passing from the higher elevation of the forebay to the lower elevation of the tail-race turns a turbine which, in turn, is directly connected to a generator. The terminals of the generator or generators are then connected to power transformers which, by virtue of their association with the power plant, are located near the adjacent bodies of water. These transformers are required to "step up" the generated voltage to the levels necessary for transmitting the energy the relatively long distances from the production facilities to the system loads. Typically, these transforms will have a power carrying capability of up to several hundred megawatts, and in order to provide electrical insulations as well as cooling, they will contain several thousand gallons of insulating oil.
Occasionally, failures will occur in these power transformers which can result in a fire, or a loss of some or all of the insulating oil, or both. In order to protect against the uncontrolled release of this oil into the environment, containment basins have been constructed under and around such units. In practice, these basins collect rain and other water which requires occasional draining. In the past, the drains have occasionally either been left open inadvertently, or have failed to close completely due to obstructions, thus providing a path for oil leakage or spillage into the environment.
More recently, insurance companies have issued Safety and Protection Regulations which call for the installation of automatic fire protection systems for these transformers. These systems are designed to respond to a fire or explosion by releasing a fire retarding substance such as water in order to prevent the fire from spreading to adjacent units or to the adjacent structures. Typically, these fire suppression systems might release up to several hundred gallons per minute of water onto such a fire. In the event of such a catastrophe, the existing containments would have to be large enough to contain not only the oil released from the transformer due to the damage of the event, but also the water released by the fire protection system. The existing containment structures are not large enough to accomplish this.
The solution to both of the above problems lies in the means by which these containments are drained. Whereas in the past, the practice was to drain the containments into the river once the operator was satisfied that the contents did not constitute an environmental threat, the preferred solution is to plumb the containment basins into a larger, central containment vessel. Typical hydroelectric generating facilities provide such an option. Such facilities are generally designed and built with a station sump into which various water sources such as generator and bearing cooling water, dam leakage, rainwater and the like, as well as the drainage from the transformer oil containment basins if they were so plumbed, might drain. Assuming that a means existed by which oil could be separated from water satisfactorily, this station sump would be an excellent containment vessel for the above purpose. The big problem to be addressed is that, by necessity, the only means of evacuating the contents of the station sump is to pump the water into the river, but only when there is assurance that the contents being pumped is water, and only water. The additional use of the station sump as a master containment for the various oil spill containment basins does add to the complexity of the sump evacuation system, and it is the solution to this latter problem to which the present invention is directed.